I have a 2000 model tory-bilt 16 hp 46 in cut not hydro. When in nutral the pully on the rear end turns but will not turn in forward or reverse. H e l p please

Hi,
I would say that you are not getting enough tension to fully engaged the transaxle when loaded. Does it kind of give a clunk when shifting to forward or reverse; that would indicated a healthy transaxle and some problem leading to it. Cannot get a parts breakdown for you off the info provided.
Peace,
Clarke